The present invention relates to multimedia computer systems, and more particularly, to scaling image signals which are used in multimedia computer systems.
Multimedia computer systems are information handling systems which combine the information handling characteristics of traditional computer systems with high quality video and audio presentations. The video presentation is provided by a video display device and the audio presentation is provided by an audio output device.
Multimedia computer systems include media sources which generate media signals. The media signals include audio signals, which are provided to the audio output device, and image signals, which are provided to the video display device. The image signals may include graphics signals, text signals, animation signals and full motion video signals. An image signal is converted to a video presentation by the display device, which receives the image signal and scans the image signal in a raster pattern across a screen of the display device. The speed with which the display device scans the image is called the sweep rate. The screen has a horizontal resolution and a vertical resolution which define display device screen coordinates. Each display device coordinate is a picture element (i.e., a pixel). The presentation from one complete scan of the screen is called a frame, or if the scans are interlaced, the presentation of one complete scan of the screen is called a field. To provide a full motion video presentation, a display device generates multiple frames per second.
It is often desirable to scale an image which is represented by an image signal so that the image may be presented on a portion of the screen of the display device (i.e., windowed on the screen). Scaling the image allows the image to be simultaneously presented with other images. An example of a system which would use a scaler is the multimedia system which is cross-referenced above.
It is known to scale an image by dropping pixels from the image signal. For example, Moore et al., U.S. Pat. No. 4,412,252, discloses a system in which dots along a line are deleted to reduce image width and lines are deleted to reduce image height. It is also known to scale an image by performing multiplication operations, using an image resampling sequencer circuit, on the image signal. For example, Eldon et al., "Using the TMC2301 Image Resampling Sequencer", TRW LSI Products discloses such a system.